This application claims the priority of Application No. 101 06 719.4, filed Feb. 14, 2001, in Germany, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a coil for an electrical machine, in particular an electric motor for a vehicle. Furthermore, the invention relates to the use of the coil for a stator of an electrical machine, a production method for a coil, and an apparatus for producing the coil.
Normally, coils for electrical machines or drives are wound from thick wire. The development in the field of electrical machines is currently aimed at achieving ever greater utilization of the coil, in particular at achieving an ever greater power and an greater torque for a given machine size. One condition for a high power density is a very compact coil.
Conventionally wound coils require a sufficiently large physical space, because of wire crossings resulting from an arbitrary arrangement of turns and layers. Such arbitrary wire crossings lead to spaces between the turns and layers, which limits the power density or the wire or conductor cross section.
It is an object of the invention to provide a coil which is particularly compact. Furthermore, a particularly simple method and a particularly simple apparatus are specified for producing such a coil.
According to the invention, a coil is provided for an electrical machine, in which an electrical conductor or a wire is wound with a number of turns, which are arranged one above the other in a number of layers, with the turns in a first layer being arranged parallel to one another, and the turns in a second layer being inclined, at a point which is predetermined, at an inclination angle, which is also predetermined, with respect to the turns in the first layer, and being arranged parallel alongside one another. This allows the turns to cross in a defined manner at a specific point, so that all the turns are arranged so that they lie particularly close alongside one another, and spaces are reliably avoided. Such a particularly compact coil allows a coil with a larger conductor or wire cross section to be formed in the same physical space, so that the I2R losses in the coil are particularly small. Furthermore, the motor or the machine may be designed to be smaller. Particularly in the case of a vehicle, this results in a reduction in weight and physical space.
The bending angle or kink angle is advantageously chosen so that the or each turn in the second layer is inclined by at least one pitch width. This allows, for example, the turns in the second layer to be arranged in the cavities or intermediate spaces in the first layer. The turns are thus arranged in a particularly space-saving manner. Depending on the type and configuration of the coil, individual turns may be inclined by more than one pitch width. The last or first turn in one of the layers is preferably inclined by the entire pitch width, which is formed by the total number of pitches in an adjacent layer. This means that the inclined turn is in this case inclined from the first turn to the last turn of the adjacent layer, in particular the lower layer, and is thus inclined obliquely over all the turns or pitches in the lower layer.
The coil start and coil end are expediently passed out jointly at one end winding, with the turns in the second layer at the opposite end winding being inclined at the bending angle. This allows the coil to be arranged in a space-saving manner, in particular in a stator of an electric motor. In this case, the end winding with the coil start and end is arranged as close as possible to the interconnection ring, with the end winding (which has the turn crossings) being arranged opposite, and hence exposed. Depending on the purpose for which the coil will be used, the bend, which can be predetermined, of the turns in one layer may be designed to alternate, for example with the first layer at the upper end winding, the second layer at the lower end winding, or on a longitudinal side of the coil. The end windings of the coil are advantageously domed outwards. This makes it possible to install the rotor particularly easily, for example in a stator of an electric motor.
In one preferred embodiment, the turns in a single layer are arranged parallel alongside one another, and partially superimposed. Such an arrangement of the turns with overlapping layers allows the coil to have a trapezoidal cross section, which allows a particularly space-saving arrangement of a number of coils in a particularly complex form, for example in a stator.
The second-mentioned object is achieved, in the case of a method for producing the coil, according to the invention in that the electrical conductor for the or each turn is bent through a bending angle, which can be predetermined, at a point which can be predetermined before the turn is wound onto a coil former. Such bending of the winding wire or conductor at a point before being wound onto the coil former means that very much less force need be applied. Furthermore, this reliably avoids any bulging caused by crossings of the turns, that is to say no spaces are formed when the coil is wound, so that said coil is as compact as possible. In one particularly advantageous embodiment, the turns in a first layer are wound parallel alongside one another, with the turns in the second layer being inclined through the bending angle with respect to the first layer and being arranged parallel alongside one another. This allows, in particular, the turns in the second layer to be arranged to avoid any possible spaces in the turns of the first layer, in that the turns in the second layer are bent such that the respective turn is arranged between two turns in the first layer, and thus in the spaces or depressions between them. Depending on the embodiment of the coil, the bending angle is chosen such that the or each turn in the second layer is preferably inclined by at least one pitch width. This results in an arrangement in which the intermediate spaces are filled as much as possible, and the turns in an individual plane are arranged in as plane-parallel a manner as possible. Undesirable crossings are reliably avoided. An individual turn in one of the layers is inclined by the total pitch width, which is formed by the total number of pitches in an adjacent layer. In particular, the first turn in a layer is inclined at an appropriate bending angle over the entire width (=overall pitch width) of the lower layer. In this case, this layer has one turn or partial turn which runs obliquely over the entire pitch width.
Depending on the application of the coil, for example in a stator of an electric motor, the coil start and coil end are preferably passed out jointly at one end winding, with the turns in the second layer at the opposite end winding being inclined at the bending angle before being wound onto the coil former. This ensures that crossings occur only on one longitudinal side or at one end winding. Thus, depending on the nature and shape of the coil, it is possible to choose that side which is advantageous for a compact configuration and arrangement for the subsequent application. In a further alternative embodiment, the turns in a single layer are preferably wound parallel alongside one another, partially superimposed. Such a trapezoidal winding makes it possible for a number of coils to be arranged in a particularly space-saving arrangement alongside one another.
A further object is achieved according to the invention by an apparatus for producing the coil for an electrical machine, in which a guide body is provided for winding an electrical conductor onto a coil former, with each turn of the electrical conductor being bent by means of the guide body through a bending angle, which can be predetermined, at a point which can be predetermined before that turn is wound onto the coil former. In this case, the guide body is preferably arranged such that it can move. Alternatively, the guide body may comprise a motor for moving two bending pins. Such an apparatus or winding machine, whose design is particularly simple, allows a coil to be wound in a particularly space-saving manner, so that it is particularly compact. To this end, during the winding process, in particular when the process of winding the coil is stopped in a defined manner at a predetermined point, the guide body is shifted by a predetermined amount for each turn, for example in a region between grippers, in such a manner that this ensures that the winding wire or the conductor is inclined in a manner corresponding to the bending angle, before being wound onto the coil former. Alternatively, instead of shifting the guide body, it is also possible to provide a motor which moves two bending pins forward per turn at a predetermined point during the winding process, and these bending pins move in such a manner that the resulting guided winding wire is inclined through the bending angle before being wound onto the coil former.
The advantages which are achieved by the invention are, in particular, that defined kinking or bending of the winding wire or of the conductor for each turn (before being wound onto the coil former) at a predetermined point on the coil, in particular at that point or in that region of the conductor which forms one of the end windings, avoids turns crossing randomly, and thus reliably avoids spaces. This results in a coil which is as compact as possible. In a compact coil such as this, a coil with a larger wire cross section can be formed in the same physical space, thus reducing losses. On the other hand, a compact coil such as this likewise makes it possible to design a motor, which is intended to hold the coil, to be smaller or more compact, thus once again allowing the weight physical space to be reduced.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.